COMMON LATTICE TYPESDOE-HDBK-1017/1-93Structure of MetalsCOMMON LATTICE TYPESAll metals used in a reactor have crystalline structures. Crystallinemicrostructures are arranged in three-dimensional arrays called lattices. Thischapter will discuss the three most common lattice structures and theircharacteristics. EO 1.2DEFINE the following terms:a.Crystal structureb.Body-centered cubic structurec.Face-centered cubic structured.Hexagonal close-packed structureEO 1.3STATE the three lattice-type structures in metals.EO 1.4Given a description or drawing, DISTINGUISH between thethree most common types of crystalline structures.EO 1.5IDENTIFY the crystalline structure possessed by a metal.In metals, and in many other solids, the atoms are arranged in regular arrays called crystals. Acrystal structureconsists of atoms arranged in a pattern that repeats periodically in athree-dimensional geometric lattice. The forces of chemical bonding causes this repetition. Itis this repeated pattern which control properties like strength, ductility, density (described inModule 2, Properties of Metals), conductivity (property of conducting or transmitting heat,electricity, etc.), and shape. In general, the three most common basic crystal patterns associated with metals are: (a) thebody-centered cubic, (b) the face-centered cubic, and (c) the hexagonal close-packed. Figure 2shows these three patterns.In a body-centered cubic(BCC) arrangement of atoms, the unit cell consists of eightatoms at the corners of a cube and one atom at the body center of the cube. MS-01Page 6Rev. 0